Circuit breaker



E C4 RANEY Nov. 30, 1937.

CIRCUIT BREAKER Filed May 22, 1954 Patented Nov. 30, 1937 UNITED STATES PATENT OFFICE Ranco Incorporated, poration of Ohio Application May 22,

9 Claims.

This invention relates to an improvement in automatic circuit breakers of the type employing a fusible release mechanism, wherein the fusing of solder, or other suitable material having a relatively low fusing point, by the heating of a heating element functions to release a latch to open an electric switch, the subsequent cooling and solidiiication of the fusible material permitting restoration of the switch to its normal position of circuit closure.

An object of this inventionis to provide an improved fuse operated circuit breaker wherein the heating element is conned substantially within the walls supporting the fusing material so that the heat released by the heating element will be applied more directly to the fusing material than was heretofore possible in fuse operated circuit breakers wherein the heating element was placed remotely from the fusing material.

Another object of this invention is to provide a heating element which can be readily inserted, removed or replaced in operative relationship to the fusing unit of the circuit breaker and wherein the construction of the fusing unit and heating element is of such character that a high degree of skill or care on the part of Workmen is not required to correctly position the heating element in assembly or replacement operations.

More specifically, my invention comprises a fusing element for retaining a biased circuit controlling member in a position of circuit closure, the said fusing element consisting of a bearing member provided With an open ended chamber, in which is disposed an electrical heating element preferably embedded in a heat transmitting dielectric substance and replaceably positioned in said chamber, the bearing member being surrounded bya toothed sleeve which is normally held against rotation on the bearing member by the interposition of a body of solder or other metal having a low fusing temperature, the solder being responsive to the temperatures developed by said heating element so that when a determined high temperature is reached, the heat released by said element will be sufficient to fuse the solder and thereby permit rotation of the toothed sleeve which, in turn, releases the circuit controlling member and allows the latter to respond to the biasing influence constantly exerted thereon and assume a position of circuit opening. The subsequent cooling and solidification of the solder permits of the manual restoration of the circuit controlling member to its position of circuit closure without substitution or replacement of parts.

Columbus, Ohio, a cor- 1934, Serial No. 726,984

(Cl. 20G- 124) For the purpose of illustrating my invention, I have chosen to describe a form of the invention applied to a manually operated switch such as that which may be used in connection with a refrigerator thermostatic control.

In the accompanying drawing:

Fig. l is a view, partly in front elevation and partly in Vertical section, showing a preferred form of the circuit breaking mechanism comprising the present invention;

Fig. 2 is a perspective View of the and releasing members;

Fig. 3 is an enlarged vertical sectional View taken through the fusing element;

Fig. 4 is a transverse horizontal sectional view taken through said mechanism on the plane indicated by the line IV-IV of Fig. 1;

Fig. 5 is a bottom plan View thereof;

Fig. 6 is a transverse section on the line VI-VI of Fig. 1, and

Fig. 7 is a wiring diagram.

Referring more particularly to the drawing, the numeral I designates a casing in which the circuit controlling mechanism comprising the present invention may be mounted. Secured in connection with the casing I by screws or the like are a pair of spaced strips which carry stationary contacts 2 which are adapted to be connected with suitable conductors 3 constituting a part of an electric circuit for the actuation of an electric motor or other suitable electro-responsive apparatus. To complete the circuit, use is made of a snap switch which, in the form of the invention here illustrated, comprises a switch arm 4 pivotally mounted as at 5 in connection with the bifurcated lower end of a crank 6, the latter being pivoted, in turn, as at 'I in connection with the casing I. Mounted o f the stationary pivot 1 is a pivotally movable curved arm I0, which has its outer end connected with a coil spring II, the latter being connected at its outer end with the forward portion of the switch arm 4. The upper end of the crank arm 6 projects through an opening provided in the top of the casing I and is equipped with an insulated manipulating portion I3. The forward or outer end of the arm 4 supports a block I4 of an insulating material which pivotally supports the intermediate portion of a bridging strip I5, which is adapted, through the movement of the switch arm 4, to be brought into and out of engagement with the spaced stationary contacts 2 to open or close the circuit with which said contacts are employed.

In the operation of this mechanism, in order to close an associated circuit, the member I3 is switch arm engaged manually and rocked about its pivot.

This imparts arcuate swinging movement to the lower part of the member I3 which is transmitted to the crank 6, causing rocking movement of the latter about its stationary pivot l. This results in swinging the pvot 5 in an upward direction without affecting the position of the. arm I0, since the curvature of the latter is sufficient to prevent contacting of the pivot pin 5 therewith during such upward movement of the pin. The upward movement, however,.of the pivot pin 5, due to the oscillation of the bifurcated lower end of the crank 6, causes said pin 5 to move past an imaginary line running through the pivot 'I and 5 the outer end of the' switch arm ll where the spring II is attached, with the result that the spring causes the arm to swing rapidly, after movement has been initiated, from its position of circuit opening to its position of circuit closure,

wherein the strip I5-of the arm l engages with the contacts 2. Likewise, the switch may be `opened by reversing the above procedure, wherein the actuating member I3 is rocked so as to effect a lowering of the floating pivot 5 so when that pivot moves below the imaginary center' line of the coil spring II and the arm Il, the latter will respond to the operation of the spring II and Will open with a rapid or snap action, removing the strip I5 from engagement with the contacts 2.

'Ihe operation so far described has been that of a manual rapidly operating snap type switch and the present invention resides in the provision of improved thermally actuated means for automatically opening the switch or oscillating the arm 4 to a position of circuit opening against the influence of the spring II when the latter functions to hold the switch arm in a position of circuit closure. To this end, the bifurcated lower end of the crank 6 has co-nnected therewith a plate I6 of liber or other current insulating material, which extends downwardly from said crank and lies in a vertical plane in the form of the invention illustrated. 'Ihe plate IS has its lower Aregion provided with an arcuate slot I'I which cooperates with a headed pin I8 projecting from a sliding latch bar4 I9. The slot I'I permits of oscillation of the plate I6 to provide for manual operation of the switch arm ll to open or close the associated circuit without aiecting the latch bar when the latter is normally positioned in a restrained state, as will be hereinafter described. Associated with the latch bar is a coil spring 20, one end of which is suitably connected with a stationary part-of the casing I while the other end ofsaid spring is connected with an apertured ear 2I formed with the bar I9. 'Ihe extreme forward end of the bar I9 terminates in a laterally bent finger '22 which is designed for cooperation with the ratchet teeth4 23 of a rotatable releasing mem- -ber 24 of the fusing element 25, constituting one of the important features of the present invention.

The fusing element comprises a bearing member 26 which is threaded as at 2l into engagement with the casing I, and surrounding the member 26 is the sleeve 24 on which the ratchet teeth 23 are formed. Interposed between the outer part of the member 26 and the inner part of the sleeve or wheel 24 is a film of a metal having a low fusing point such, for instance, as solder, as indicated at 28. When the metal 28 is in a solid state, rotation of the member 24 relative to thebearing member 26 is prevented, but when the metal is heated to its melting point and becomes substantially uid, and its grip on the sleeve 24 is weakened the latter may rotate by reason of the pressure of thespring 20 in order to effect the release of the latch bar I9 and the rearward propulsion of the` latter, through the contraction of the spring 20. This brings the headed pin I8 of said latch bar into contact with one end of the slot I'I thereby rocking the cran-k 6 and the switch arm 4 to effect the movement of the latter to its position of circuit opening.

To regulate the melting -of the solder or other equivalent body 28, the bearing member 26 is provided with an open-ended chamber 29 in which in positioned a heating coil 3U, the latter being embedded in a body 30a of a heat conducting dielectric such as heat treated magnesium oxide. The dielectric serves to space the convolutions of the coil 30 and prevents deformation or short circuiting of current through the same and also serves as a heat conductor` for transmitting the heat of the coil to the walls of the chamber 29. 'Ihe heating coil 3U and the dielectric in which it is embedded are supported by means disposed eX- traneously` of4 the member 26, and ,preferably by means of the lateral extensions3 Ia and 3l b. The extension 3Ia constitutes a part of an attaching plate 3 Ic which is connected with one of the contacts 2 by means of the screw 3Id, while the extension SIb is connected with one of the conductors 3 by the screw 3Ie. By loosening the screws 3| d and 3| e, the heating coil and its dielectric may be readily removed from the assembly and likewise conveniently replaced. It will be seen that if the circuit should be overloaded for any reason, an excess amount of heat, above a determined normal operating temperature, will be released from the heating coil. Since the latter is located axially within the chamber 29, the heat released therefrom will be applied directly to the walls of the bearing sleeve by means ofthe heat conducting dielectric material. and thence to the body of low fusion metal 28. If this temperature rises to undesired limits, it effects the melting of the fusible metal 28 and the consequent loosening of the ratchet wheel 24 and the actuation of the switch arm to open the circuit. When normal operating temperatures are restored, the solder solidies which allows of the manual restoration ofthe parts of the apparatus to normal positions of circuit closure. The heating coil may be quickly replaced by reason of the open-ended construction of the bearing sleeve. It will be seen that the heating coil may `readily be replaced by4 a coil having a different current carrying capacity without the use of special tools or skill on the part of the workman. Moreover, the heating element or coil is disposed mainly Within the confines of the sleeve formed by the solder film 28, so that the latterwill be quickly and readily influenced by the heat of said element or coil in responding to'high or abnormal, overloading currents. Thus overheating of the coil 3U results in the transference of heat, in a manner substantially independent of extraneous thermal condition, by conduction through the dielectric body 30a and thence through the relatively thin wall of the bearing 26 to the sleeve of solder or other low fusion point metal.

This construction, therefore, provides a release which is positive and eiectual, within close operating limits, is not affected by ambient atmospheric conditions, cannot lose its operating positions and may be readily installed or replaced.

What is claimed is:

1. In a fusible control unit for automatic circuit breakers, a bearing member formed with a chamber, an electric heating element, a solid heat transmitting dielectric substance removably positioned in said chamber and in which Said heating element is embedded, a releasing-member carried by said bearing, and a body of solder uniting said releasing member with said bearing.

2. A fusible control unit for automatic circuit breakers, comprising a bearing provided with an axially disposed open ended chamber, a heating element embedded in a dielectric heat transmitting body removably disposed in said chamber,

a releasing element mounted on said bearing, and

a body of solder interposed between said releasing element and said bearing.

and operable when below a determined tempera- ,I

ture to preclude relative movement between said releasing element and bearing member.

4.*In a fusible control unit for automatic circuit breakers, a bearing member provided with a socketja plug formed from a heat transmitting dielectric substance replaceably positioned in said socket, and an electrically energized heating element embedded in said plug in heat transmitting relationship with respect to said bearing member. 5. In an automatic circuit breaker, a bearing provided with a chamber, a release means rotatable about said bearing, abody of metal having a low fusing temperature interposed between said bearingand release means, and an electrically heated element disposed within said bearing chamber mainly within the connes of the body of metal having a low fusing temperature, said heating element being electrically spaced from said bearing. e

6. A fusible control unit for automatic circuit breakers comprising a bearing member provided with an internal chamber open at one end, a cylindrical body of dielectric material removably positioned within the chamber in said bearing member, a resistance coil embedded in said cylindrical body with both terminals thereof projecting from one end of said body, a releasing element surrounding said bearing member, and a thin tubular body of solder uniting said releasing element with said bearing member.

7. A fusible control unit for automatic circuit breakers comprising a bearing member having a shoulder at one end and an internal bore open at the shouldered end of said member, a

ratchet member surrounding said bearing member and resting upon said shoulder, a lm of readily fusible metal uniting said ratchet'member and bearing member, and a resistance element embeddedin a body of dielectric material with both terminals thereof protruding from one end positioned in the bore in said bearing member.

`'8. A fusible control unit for automatic circuit breakers comprising a bearing member with a threaded shoulder at one end and an internal bore open at the shouldered end, a ratchet surrounding said bearing member and resting against said shoulder, a film of readily fusibleV metal unit- I ing said ratchet and said bearing member, a.

cylindrical body ofv heat transmitting dielectric material removably positioned in the bore in said bearing member, and a resistance coil embedded in said cylindrical body with both terminals thereof extending from the same end.

, 9. A fusible control unit for automatic circuit breakers comprising a bearing member formed with an axial open-ended chamber, a ratchet member surrounding said bearing member, a iilm of readily fusible metal uniting said ratchet and bearing members, a body of dielectric material removably positioned in said chamber, and a resistance coil embedded in said dielectric body with both terminals extending from the same end.

ESTEL C. RANEY. 

